Sunday, March 29, 2009

9/11 "Truthers" Meet their Waterloo - The Ron Craig Talk

The UW 9/11 Research Group, which previously sponsored two presentations by truthers, has finally gotten around to hearing the other side.

Ron Craig, a professor at Ryerson University with extensive training and experience in explosives, gave a talk Friday night in the Arts Lecture Hall at the University of Waterloo. Here's a brief summary:

He started by asking, "How many people here believe the WTC buildings were brought down by explosives?" Sadly, about half the people in the audience of approximately 100 raised their hands.

He then showed clips of the WTC buildings collapsing, some eyewitness testimony, and excerpts of last year's appalling presentations by A. K. Dewdney and Graeme MacQueen. He then asked rhetorically, "After seeing all this, how could you not believe the towers were brought down by explosives?"

Briefly, his answer was "expectation bias": investigators reach a premature conclusion without examining all the relevant data.

9/11 "Truthers" start with a presupposition, then look for data to support it. By contrast, real fire investigators start with documents such as NFPA 921, which outlines a scientific basis for investigating these incidents.

Craig pointed out that the WTC buildings used an innovative design for lightweight construction. They were the first super-high buildings to use this kind of construction, without heavy girders. The buildings weighed only 1/2 of what a conventional building would have weighed.

When demolition experts want to bring down a building, he said, they drill into columns and place the explosives. But no cement columns were used in the WTC. Furthermore, maintenance at the buildings reports that core beams above the 84th floor were inaccessible.

He then examined one claimed scenario for controlled demolition: in this scenario, explosives were placed on every floor. He then estimated how much explosive would be needed in this scenario, and came up with 1300 pounds of TNT-equivalent per floor, for a total of 143,000 pounds. Clearly this would be infeasible to set up without someone noticing.

Furthermore, such a large amount of explosive would have blown out windows in other buildings for blocks around. But this did not occur. In an explosive detonation, the typical inury is from flying glass, but there is no evidence that this occurred, nor evidence of other kinds of projectile injuries.

Explosives create heat of as much as 7000 degrees. Thermal injuries will be accompanied by primary blast injuries caused by pressure when the shockwave progesses through the body (e.g., middle ear injuries). "Blast lung" can occur at 50 to 150 psi. But not a single person in NY exhibited any symptoms of PBI.

Claims that thermite was used is undermined by the fact that no barium nitrate was found in the debris. He estimated that 61,000 pounds of thermite would have been needed. Again, it would have been impossible to set this up without someone noticing. Claims that sulfur was a signature of thermite/thermate are silly, because both the elevator shafts and stairwells were constructed with drywall, which is gypsum (calcium sulfate with 18% sulfur content).

Claims that molten steel was still flowing 21 days after the attacks are implausible. He showed one slide that supposedly depicted white-hot metal being observed by workers; it was actually just a worklight, as a video showed.

There is no good evidence that there were pools of molten steel. Many metals were at WTC, and low-temperature alloys could easily have formed. NFPA 921 says "if this occurs it is not an indication that accelerants were used or were present in the fire."

He then addressed the claim that "no other steel frame building has ever collapsed because of fire". He addressed other fires, such as this one at Delft. During the fire there was a partial collapse with "squibs" visible just as in the WTC.

He compared the WTC fire to other fires, such as the one in Madrid and One Meridian Plaza in Philadelphia. Both of these buildings had designs quite different from WTC.

Overall, I'd rate this part of the presentation as an A-. I think his points were very effective, although he could have also referenced the 1967 McCormick Center fire in Chicago, and he could have pointed to the lack of seismic evidence for explosions.

After the talk, there were some questions from the audience. One questioner asked him if he considered the "geo-political context" for 9/11. To his credit, Craig said that this was not his area of expertise; he is a fire and explosives expert, and his job is to look at the hard evidence, not speculations about motives.

Another questioner suggested that the Towers were brought down by some high-tech explosive invented by the government but unknown to everyone else. Craig found this suggestion (and a similar suggestion that "lasers" were used) ridiculous, saying that he regularly attends explosives conferences and such a thing could not be kept secret from experts.

Another questioner brought up the collapse of WTC 7. Craig said that he did not know for sure the cause of the collapse of that building, because not enough evidence was gathered yet. He said that he expects we will eventually know, because there is a strong motivation by architects, engineers, and insurance companies to understand the reasons behind the collapse, and many people are working on it.

I'd rate the question-answering portion as B+. Sometimes he simply reiterated previous points, instead of attempting to address the question from another angle, but overall he was generally effective.

Overall, I thought Ron Craig did a good job of demolishing the bizarre and unsupported claims by truthers that explosives brought down the World Trade Center buildings. Regrettably, it is unlikely to have much impact on truthers, who typically hold their beliefs with a religious fervor.

There was a show on PBS (probably Nova) several years ago that examined why the buildings collapsed. As I recall, they were designed to withstand the impact of a Boeing 737 but may very well have remained standing after being hit by the larger aircraft had not the heat of the burning jet fuel sufficiently softened some horizontal steel members that held it together.

The Myth of Controlled Demolition in the Collapse of the WTC Buildings

It is amazing to me how many Architects and Engineers cannot understand how the Towers could collapse from fire. WTC 7, a high-rise office building was not hit by any planes and was destroyed by a fire in ordinary combustible furnishings. You may say it’s highly unreasonable to believe that 4 steel constructed high-rise buildings collapsed from fire in one day? Well they all had one thing in common; Long Span steel composite floors with connections not designed for thermal effects. They designed these buildings to maximize office space while maintaining exterior views and providing office layout flexibility and the interior columns were interfering and had to be removed. This column removal was attained by using long span steel beams and girders which are used in many existing office high-rise buildings. The use of long floor spans along with the 1968 building code relaxation lowering the fireproofing requirements have apparently created a condition that with large fires in these buildings could lead to a major collapse. Long span steel beams have a magnified response to heat. They expand a longer distance than short span beams and they still have their full strength in the beginning of the expansion. NIST computer studies show that this strength while the beam is elongating can shear off the bolts connecting the beams to the columns or girders if the connections are not designed to counter this effect. This strength as the beam expands can also crack the concrete slab at the shear studs and buckle the beam itself as differential internal compression builds up in the steel during expansion. A buckled or bowing long span (over 40 feet) beam can impart large tension forces on the connections especially when a sagging beam begins to shrink as it cools. Bowing occurs when the bottom flange of a steel beam expands faster than the top flange. Bar joist floor bowing places immediate pull-in tension on the connections.

The performance of the floor/beam systems in such buildings has been attributed to a complex interrelated sequence of events, described rather simply as follows (Buchanan 2001):1. The fire causes heating of the beams and the underside of the slab.2. The slab and beam deform downwards as a result of thermal bowing.3. Thermal expansion causes compressive axial restraint forces to develop in the beams.4. The reaction from the stiff surrounding structure causes the axial restraintforces to become large.5. The yield strength and modulus of elasticity of the steel reduce steadily.6. The downward deflections increase rapidly due to the combined effects of theapplied loads, thermal bowing, and the high axial compressive forces.7. The axial restraint forces reduce due to the increased deflections and thereduced modulus of elasticity, limiting the horizontal forces on thesurrounding structure.8. Higher temperatures lead to a further reduction of flexural and axial strengthand stiffness. (NISTIR 7563)9. The slab–beam system deforms into a catenary, resisting the applied loadswith tensile membrane forces.10. As the fire decays, the structural members cool down and attempt to shorten in length.11. High tensile axial forces [pull-in] are induced in the slab, the beam, and the beam connections.These actions can take place in two or three dimensions

Photo of Steel structure after Cardington tests in the UK

Use of Steel in Construction

Steel has always had a stability problem under fire conditions. Steel members begin to expand immediately when heated and internal thermal stress in the beams, girders, or joists bends, buckles, twists, and warps the steel, eroding structural integrity. Thermal expansion in a long span beam can shear off the bolts connecting the beam. Thermal contraction in a sagging, long span steel beam can tear out the connections as the beam cools. From a collapse potential the long span, bar joist trusses used in the Tower construction was a most vulnerable design. It was evident from the bowing inward of the exterior columns that the sagging trusses pulled-in these columns on the long span side of each building beginning the progressive collapses. There is also evidence that the collapse timing corresponded with the time to heat these steel trusses,- depending on the insulation thickness used in each tower,- to a temperature which expanded the steel enough to collapse the trusses or cause thermal bowing where the lower truss chord expands allowing the top chord to go into suspension, or upon cooling of the sagging contracting trusses pulled in the exterior column walls .

UK engineer Dr. A.S. Usmani, et al., related the following relative to his preliminary findings about the collapse of the WTC Towers: 5

Due to their length and slenderness, the thermal expansion effects in long-span, steel bar joists produce compression buckling in floors at lower temperatures than are presently compensated for in the fireproofing codes. This sort of thing has not been considered in the design of high-rise structures, with the possibility of multiple-floor fires.

Longer-span steel structural members expand a greater distance than short-span elements, and, as they are heated, slender elements can fail from buckling under compression at temperatures that are still low enough (400° to 500°C) that the steel retains most of its strength.

According to S. Lamont et al “The furnace test does not consider vial structural phenomena found in the 3D behavior of real buildings including large deflections, restrained thermal expansion and thermal bowing, membrane and catenary load carrying mechanisms in slabs and beams respectively, and compatibility of deflections in two or more directions in an integrated structural frame,”41

Expansion Effects

The wider floor sections of the Towers had longer 60 foot joists, which, because of increased loads, would be inherently weaker and would expand and lengthen a greater distance if exposed to heat. Note: “Steel will expand .06 percent to .07 percent in length for each 100°F rise in temperature. Heated to 1,000°F, a steel member will expand 9½ inches in 100 feet of length.” 21 According to the FEMA, ASCE- Building Performance Study, “an unrestrained, 20-meter-long [about 60-foot] steel member that experiences a temperature increase of 500°C [1,022°F] will expand approximately 110 mm [4.0 inches].”18 Note: Steel expansion begins immediately as the steel is heated and can be destructive to the long span trusses even though the steel temperature is low enough (300 to 500 C) that the steel retains most of its strength.

“Differential expansion of steel is probably the main cause of failure of the floor system used in the towers. Since the top chord of the long-span truss is steel, it will elongate more than the top concrete slab at the same temperature. Steel, if not adequately insulated, will also absorb heat faster than concrete. Steel differential expansion has been shown to be a cause of bowing, shear-induced buckling of the struts and the loss of composite action in the floor system [as a result of] the shear ‘knuckles’ detaching from the concrete. The knuckle bonds sequentially break, starting at the ends, eliminating the composite action under load. “(NIST, 2, Appendix K):

Current practice is to protect the steel by requiring enough insulation to prevent loss of strength by preventing columns from reaching 1000 deg. F (538o C) and beams from reaching 1100 deg. F (593o C) in the standard furnace test. This criterion has proven effective in short span designs. As the steel is heated further and temperatures rise to higher than 600°F, steel loses strength. At 1,200°F (about 650°C), steel loses about 50 percent of its strength. At 1,300°F (about 700°C), the yield point is drastically reduced and steel members fail. The collapse of Building 7 and the Twin Towers has been proven that this protection requirement (i.e. 10000 F. for columns and 11000 F for beams) inadequate when protecting long span steel floors since the expansion effects in steel beams can buckle the beams or fail the connections at lower temperatures (400 to 5000 C). Long span steel must now be protected from heat by adequate fireproofing insulation and integrated properly to compensate for the lower temperature effects of thermal expansion and contraction during fires. To maintain building stability, lateral bracing becomes even more important in construction that features lightweight, long-span floors. All three buildings relied on floor membrane stability to laterally support the columns.

The fireproofing insulation thickness schedules in the Building Code were developed for the short span floors which were used in the older high-rise buildings and this insulation defended against thermal weakness in the steel beams rather than expansion which apparently was not a problem in the shorter spans. Steel weakening occurs later at higher temperatures 1100deg. F (about 600 deg. C). Low temperature expansion effects occur earlier as the steel is first heated to temperatures below 400 deg. C and long span, expansion effects have yet to be compensated for in the fireproofing insulation codes. This deficiency in high-rise office buildings using large open areas, and long span composite flooring systems is a new finding uncovered by the study of the collapse of the Twin Towers and Buildings 5 and 7 and was first illuminated in the engineering computer studies. Further scientific research is critically needed to determine what changes are needed in fireproofing insulation types and schedules for the longer spans and the possibly of requiring span limitations, redundancies in column strength, connections designed to compensate for the expansion and separate lateral column support.

A key characteristic of large open office areas not compartmented by firewalls is that a fire can release a large quantity of heat as the fire spreads over the floor if not extinguished immediately as by a working, water spray system (sprinkler) or by the Fire Department. The water spray systems in both towers and Building 7 were damaged by the forces of plane impacts and in Building 7 by the tower’s collapse impacts damaging the water mains in the streets which also deprived the Fire Department of water. Fire size is another major factor affecting steel failure. FDNY Chief Vincent Dunn explains:

“A large-area fire in which flames involve much of the steel beam in a short period of time will heat a beam to its critical temperature more quickly. A so-called ‘flash fire’—which suddenly involves a large area with flame, can heat [inadequately fireproofed] steel to its failure temperature rapidly.”4

Because long span, lightweight steel, bar-joist floor construction was used to provide wide-open spaces free of columns within the WTC towers, vulnerabilities were introduced. Since lightweight steel trusses are affected by a large fire faster than heavy members, and since they span such larger areas, their failure would be much more serious than would the failure of a short-span element.

The other thing about long span floors is that when an interior column or columns fail under such large area circumstances the building may not be able to redistribute the floor loads to other columns and the collapse is likely to progress upwards putting all the floors above into suspension. If the building is not protected against progressive collapse, global (total) collapse can ensue. Building 7 collapsed because one key interior column failed after the long span floors failed around it. Because of the long spans the key column was supporting a large area of flooring on every floor. It was discovered by the NIST computer studies that failure of this one column would have brought the entire building down without any fire. Such a lack of column redundancy should be corrected by deigning the building to withstand the removal any single column.

Reports of Controlled Demolition, Molten Steel, Thermite, etc.

Scientists rarely speak of the ‘truth’ until they have spent enough time examining the evidence. Its amazing to me how the Architects and Engineers for 9/11 Truth who apparently have little or no knowledge or expertise in fire protection or building collapse, just dismiss the reports of the top Fire Protection engineering experts in their fields and take some theological professor’s absurd babble as gospel. I suppose if their car’s engine broke down they would call the local preacher. The vaguest possibility is immediately touted as the truth and repeatedly echoed on the internet without any research or fact checking. Four years after the 9/11 attack and without inspecting any of the steel the Architect Richard Gage was listening to some equally uninformed Philosophy Professor, David Ray Griffin and had an epiphany and from then on he ‘knew’ that the buildings “had to be brought down by explosives”. “That’s the only way that you could have all the exterior columns in Building 7 fail within a fraction of a second.” How does he know all the columns failed at the same moment? These lower columns were out of sight of the cameras. The first thing to fail was the floors on the east side then the east interior columns as evidenced by the east penthouse on the roof caving in. Five seconds later the west penthouse caved in indicating widespread core column failure and than the exterior frame started to descend, but the outside frame was strong and there were large belt trusses around the entire building between the 22nd to 24th floors. These belt trusses held the upper building steady until a large number of lower exterior columns had failed. With the failure of most of the interior floors and columns there apparently was an 8 floor section of exterior columns without lateral support. When this 8 story section of columns buckled the building began a 2 second period of free fall acceleration. Building 7 took over 13 seconds to collapse not 6.

NIST computer models show that the building was deconstructed by the heat of the uncontrolled fires expanding the long span steel floors, buckling the beams, disconnecting structural steel, and eventually buckling one key column which started the progressive collapse. The design was so flawed that that because that one column buckled the collapse progressed up to the roof and than across the core to take down the entire interior of the building. I want to hear what the Architects & Engineers for 9/11 truth think about a building within which the failure of one column will start a progressive collapse that brings down the whole building. Now that’s an architectural and engineering problem that needs their attention which will not be forthcoming if they continue to believe the buildings were taken down by supposed explosives. The Architects and Engineers for 9/11 truth’s Richard Gage is going all around the country spreading his pseudoscientific misinformation that explosives were used to bring down these buildings.

The top experts in the field, Shyam Sunder the NIST lead investigator, Gene Corley the American Society of Civil Engineers lead investigator both of whom have years and years of engineering experience believe the buildings were brought down by the fires. Gene Corley who was also the lead investigator in the Oklahoma City disaster, - which was destroyed by explosives, - said there was “no evidence of explosives” at the WTC site. He and Johanthan Barnett another experienced Fire Protection Engineer were on the scene immediately and examining the steel. Dr. Barnett described the devastation caused by the interior collapse of several floors in Building 5 (Yes. Building 5.) from fire when the steel beams pulled out from their connections. These are all recognized experts in their fields and have to get things right in order to maintain their positions. I doubt a person inexperienced in the fire protection field could prove them wrong on anything related to the towers collapse without years of study, but they keep trying. The BBC put on the top building demolition expert Mark Loizeaux who explains how the towers collapse could not have been a controlled demolition and all he gets is blasted by the 9/11 ‘truthers’ for being ‘in-on’ the conspiracy.

Their spokesperson Kevin Ryan knew very little about how floor assemblies are tested by his own company Underwriters Laboratory. He worked in the water testing section of the UL. Mr. Ryan reported that they tested the steel and it withstood 2000 deg for 3 and 4 hours. The UL tests 17 foot floor and wall assemblies not the steel per se. The problem is that the long span composite floors used in the towers were never tested by anyone in their long span configuration of 60 feet. Building 7 also used long span steel “I” beams. What most architects apparently don’t yet know is that lightweight, long span steel trusses and “I” beams can fail at fire temperatures not yet compensated for in the codes. The standard furnace test can only handle 17 foot lengths of flooring and doesn’t test the connections for fire exposure. The furnace standards were set in the 1930s, 40s, and 50s when about 15 to 20 feet was the standard span used in high rises built for the more conservative codes at that time. These older buildings used shorter spans, more robust columns and beams, stronger connections and better fireproofing then now and stood up to fires quite well. If a floor failed the push-out forces of expansion and the pull-in (catenary) forces created by the short spans were easily handled by the strength of the rest of the structure. For this reason the codes allowed floors to have a shorter (3 hour) rating than the columns and girders (4 hours). The 17 foot furnace test, currently still used, is meaningless for the longer spans and connections. The main problem in the Tower flooring was due to the differential elongation (expansion) of the steel parts of the trusses.

NIST’s studies found that the different expansion rates immediately deformed the steel parts, buckled the top chords and struts in the bar joist floors and disconnected the composite bond between the concrete slab and the steel joists. Greater thermal expansion of the bottom chords releases the tension and allows the cool top chord to sag and bow downwards until it acts as a cable in suspension creating pull-in forces on the columns. Buckling of the top chord allows the bottom chord to act as a catenary. The contraction of sagging, long span steel flooring during the cool down faze after the fire dies down puts heavy pull-in loads on the connections. It is now known that Building 7 collapsed from expansion and/or contraction in the floor beams disconnecting enough of the beams and girders to affect column stability. There was a second or two when the perimeter wall came down at free fall acceleration but this in no way indicates demolition was involved. There was so much destruction of the interior structure over many floors that long sections of exterior columns failed at essentially the same time.

Many people interpreted the loud sounds and debris being projected out sideways during the Tower collapses as an indication that explosives were used. Most of these loud sounds, heard during the collapses were heard after the collapses began. In order for an explosion to cause a collapse it would have to occur before the collapse. Some ‘thunder’ sounds were heard in Building 7 before the exterior columns buckled and these were probably from floors collapsing and impacting the floors below. Explosive forces great enough to destroy the columns would be as loud as ten times the decibel level (140 db) of standing next to the speakers at a rock concert. NIST reports such loud sounds were not heard nor recorded in the video tapes.

The undamaged exterior walls can be seen bending and buckling inward in the videos of both WTC Towers long before any sounds or ground vibrations occurred. In Tower 2, the exterior columns in the east wall were photographed bowing inward up to 10 inches, 18 minutes after the plane's impact. That's 38 minutes before the global collapse began. To be technical, you could say that Tower 2's collapse began slowly, with possibly some noise or impact sounds from falling floors, about 38 minutes earlier than the official collapse time.

Sequence of buckling of Tower 2’s East wall columns.

The explosive sounds and expanding dust clouds occurred just after the east wall buckled inward and started the collapse, and not before the buckling, as would have had to have happened with controlled demolition.

When the undamaged south exterior wall of Tower 1 was photographed it was bowing inward up to 55 inches on floors 95 to 101, about six minutes before these columns were seen buckling inward. This bowing and buckling was witnessed and video taped by the Police Aviation Unit.

In the North Tower "thunder" sounds were heard when some floors apparently collapsed on the south side 12 to 14 seconds before the top of the building was seen to tilt southward and begin falling as a unit starting the global collapse. Since each section of floor on the long-span side weighed about 500 tons, I would take these 'supposed explosive' sounds in Tower 1 as evidence of a floor or floors detaching and impacting the floors below on the south side which most probably accelerated south column wall failure. The boom, boom, boom, boom, boom repetitive sounds reported by firefighters as Tower 2 was coming down were most likely caused by the sequential collision of impacting floors after the top of the building began falling. The great quantity of air on each floor being compressed in a fraction of a second by great weight and momentum would propel air, smoke, and any concrete dust and debris outward from the building at great velocity by the bellows effect of the floors coming together so quickly.

Initial Collapse Cause

Much consternation has been expressed because of the fact that NIST only analyzed the events up to the point where the Towers were poised to collapse before runaway collapse began and failed to pursue the remaining collapse. This was largely because once the collapse began the chaotic impacts of the floors, walls and columns colliding could not possibly be analyzed accurately with even the strongest computers. As it was, it was a severe strain on computer capabilities to analyze the mechanism of collapse up to the point of runaway disintegration. By dint of computers running for extended periods of time NIST did analyze almost the complete collapse sequence of building 7.

Bar joist Floors

It is clear from the computer studies that the heat from the fires caused differential expansion of the steel parts in the long span, floor trusses in the towers with the resulting thermal bowing in some floors directly exerting pull-in forces on the exterior columns or this thermal bowing could have detached a floor at the weak, single bolt connections which would have impacted the floor below destroying its composite action by separating the concrete slab from the trusses and inducing strong tensile (suspension) forces in the double weighted floor. In other floors thermal expansion of the floor against the columns compressed the trusses which along with shear forces within the trusses buckled the diagonal compression struts collapsing the trusses themselves which went into suspension (catenary action) and this also assisted pull-in and eventually buckled in the exterior column walls. Differential thermal expansion of the concrete slab and the steel has also been shown by NIST to disconnect the knuckles (knuckles are the steel tops of the bent over bars in the trusses which are imbedded in the concrete) from the concrete slab causing loss of composite behavior in the floors.

All these adverse floor effects were caused by steel expansion which begins immediately as the steel is heated. Bowing and buckling can happen at low temperatures (300 C to 500 C) even before the steel beams would have been weakened excessively from higher temperatures. The longer the beam the further it can expand and since the steel still has its full strength the expansion can break the bolts holding the beam and bow or buckle the beam itself. Thermal contraction caused by cooling of sagging trusses or ‘I’ beams after the fire ‘burns out’ or dies down can cause strong pull-in forces on the exterior columns and core columns due to the contraction of the sagging steel trusses or ‘I’ beams.

Columns

In order for a column to support the loads it has to be plumb and in line with the columns above and below. The fact is, columns have to be axially (in line and centered) aligned to support the weight of the building above. If they get out of alignment by 10 to 20 degrees they buckle and can no longer support the weight. The Tower buildings collapsed because the floors first caved in from restrained thermal expansion and from thermal bowing or delamination of the slab and bar joists composite action affecting floor truss stability. The sagging, 60 foot long, floor trusses gradually pulled-in the 59 columns in one exterior wall in each tower and these column walls eventually buckled removing practically all support on one entire long span side. In Building 7 floor failures from steel expansion and/or contraction disconnecting the floor beams exposed a critical column to loss of lateral restraint over many floors and lateral forces causing the column to buckle and remove support for all the floors above and starting the complete progressive collapse of the building.

In the WTC Towers once the exterior columns buckling spread, along an entire wall removing support on one face, the buckling spread around the towers exterior and into the core and the towers began to tilt. With the entire top of the building tilting all the columns were out of alignment and buckling and the leaning top sections of the tower began to fall straight down. Although the North tower antenna appeared from some northern angles to have began falling straight down it actually first tilted to the south because the south wall buckled first and the cantilevered top building section pulled the core along with the entire top over to the south. This is especially telling as evidence of fire induced collapse since all the damage from the plane impact was on the north side which side should have collapsed first,- if the plane damage was contributory,- and the tower should have leaned over to the north. The South Towers’ top tilted to the east because its east exterior wall buckled first from the pull-in forces of the failing long span flooring trusses on that side. Once the tower’s tops began tilting all the columns across the buildings would be out of alignment and easily buckled.

There have been some engineering analyses about the impacting floors slowing down the collapse so that the time to collapse should have been much longer than 'free fall' times of an object dropped from the towers tops. Once the buildings started to tip over from loss of column support on one side, the tremendous excess eccentric weight began buckling all the columns across the building. Once the tilted tower’s tops began descending the columns hit the floors or the lower columns at eccentric angles which easily detached the floors and buckled the columns. In order for the lower building section to offer any meaningful resistance to the falling building top, the columns would have had to hit each other exactly in line and plumb and this was impossible with the top of the building leaning causing eccentric angles of impact.

Once the Towers top building sections began tilting the columns on the side that originally buckled did not line up at all. These columns would have been hitting the floors and would have easily detached or buckled them. After the east wall buckled in Tower 2, the adjacent perimeter wall columns buckled from overloads and the columns on the opposite, west side of the building acted as a hinge would still be bearing on each other but at an eccentric angle which means they also would have also eventually buckled as the top tilted. These columns along with some of the core columns as they buckled are probably what kicked the bottom of the top building section to the west as reported by NIST. Because of the weight of the accumulating collapsing floors, there was a release of incredible potential energy changing to kinetic energy and building momentum as the accumulating chaotic mass of debris accelerated into the cellars. The heavy core columns depended on the floors for lateral support once they lost lateral support and experienced ‘pull in’ forces and got out of plumb, there would have been little resistance to their buckling at the weak splices. After the upper part of the buildings began descending, with the incredible weight of the top of the buildings’ gaining momentum, like a heavy wedge or sledge all it had to do was break the welded, and single bolt connections holding the floors to the columns.

This is coupled with the fact that the falling top section’s momentum increases as the square of the number of floors impacted as the floors were detached and added to the weight of the descending top. There would have been little resistance to slow the top section's increasing mass of impacted floors acceleration to the ground. Because this acceleration due to gravity increased the speed and momentum of the collapsing floors and building top, the impacts were increasingly violent as shown on the seismic graphs; increasing in amplitude until maximum when the mass of accumulating impacted floors hit bedrock seven stories into the cellar.

Since the Tower's outer wall columns, especially in Tower 1, pealed out like a banana after the building top began to impact and disconnect the floors, these wall columns may have been able to break the connections to the floors ahead of the floors being impacted? In other words, with the weight of the wall columns pealing outward from the vertical along with the added horizontal forces of impacting floors projecting smoke and debris outwards onto these columns, these columns, while leaning out, might have been able to break the wall-to-floor connections ahead of the level of impacting floors or with the excess strain the connections could have failed sooner. If this is possible than I believe that the connection failures could have traveled down the sides of the buildings and accelerated faster than free fall. This might explain the rapidity of the collapses especially in Tower 1. The wall-to-floor connection failures could have traveled down the building sides and in effect started the floors falling before they were impacted by the accumulating mass of impacted floors above. Anyway this mechanism would have surly reduced the failure times of the floor connections.

But these buildings did not collapse faster than free fall times and this is proved by the photos themselves. It can be seen that the detached exterior walls which were falling at free fall acceleration after they detached, were falling faster than the remaining center portions of the buildings. This fact proves the Towers fell slower than free fall acceleration.

The heavy exterior wall columns in the 1500 foot high buildings while pealing off could project the column sections outwards a great distance. This distance (300 to 400 feet) was proposed as only being made possible by explosive forces. I disagree. If a wall is strong enough and doesn’t break up as it falls outward it can fall out flat to a distance equal to its height. The Tower walls, however, did break at the weak column splices as they fell.

The compression of the 12 foot chunk of air on each floor down to a fraction of an inch in a fraction of a second as the floors came together would propel the air smoke and dust outward from the building at great velocity. The lightweight aluminum cladding as it broke free from the buckling columns also would have been propelled outward a great distance by this expanding cloud of air, smoke and dust. This gas compression would account for huge dust clouds and pieces of aluminum seen projected outwards from the upper sections of the collapsing buildings.

The light reflected off the aluminum pieces at the north wall of Tower 2 were interpreted as flashes from explosive 'squibs'. These pieces of aluminum broke off from buckling columns. The flashes below the buckling east wall may have been from the aluminum cladding breaking free from the lower columns as they expanded after being unloaded of axial compressive weight by the buckling of the wall above and their expansion breaking the connections to the cladding. Also explosives leave characteristic tears and fractures in steel and especially in aluminum, and such indications were not found anywhere in the debris pile.

The compression of air in the elevator and air-conditioning shafts by the collapsing upper building section and floors, would project air, smoke, and dust down these shafts and out any path of least resistance on any floor or any of the HVAC air intake or discharge openings on the lower mechanical equipment floors in the exterior walls. This accounts for the plumes of smoke seen projecting outwards sideways from the buildings well below the collapsing floors. There were quite extensive Heating, Ventilating, and Air Conditioning (HVAC) shafts built into the building. These vertical shafts are connected to air conditioning exhaust and intake ducts open to the exterior on the mechanical floors.

Deep Seated Pockets of Fire

After any fire in which a building collapses, there often remain pockets of fire deep within the rubble pile. These ‘deep seated pockets of fire’ sometimes cannot be reached by water streams because of their being covered by debris. Air is sometimes drawn up from the bottom of the pile and feeds these inaccessible fires with air because these natural convection currents. Heated air rises because of its expansion and resultant buoyancy and is replaced by cool air drawn in from the bottom and sides of the fire. This air flow can become rapid because of the high temperatures developed. The more air drawn in the hotter the fire becomes and the increased temperature increases the convection currents which draw in more air. After a collapse there is more combustible material available to feed the fire. Like in a furnace the containment of heat by insulation provided by the compacted combustible material surrounding the fire allows the gradual increase of temperature. I am convinced that temperatures of over 2000 deg F. can easily be developed in these deep seated pockets of fire in the rubble of a collapsed building. This temperature is still incapable of melting steel unless there is excess oxygen available.

These fires can last for days and the heat can become intense and can heat any steel in proximity to the fire until the steel is glowing red, orange or yellow hot. These pockets of fire are common at burning building collapses and in no way evidence that that explosives or thermite were used to demolish the buildings. These underground fires are similar to blacksmith forge fires where air is blown into the charcoals by a bellows to raise the temperature of the fire to heat a piece of steel or iron. The blacksmith can tell how hot the steel or iron is by its color and can tell when the steel is soft enough to work it with a hammer.

I talked to a blacksmith at Old Bethpage Restoration on Long Island and he told me that he can create enough heat to burn and melt the steel and it sometimes happens when he is talking to people and absent mindedly keeps pulling the bellows chord and feeding air into the coals. Burning the iron melts the steel and ruins the work.

"With bellows blowing additional air through the fire, it can reach temperatures of about 3,000° Fahrenheit. Iron burns at 2,800°, however, so the smith has to be careful to not ruin his work! … The smith's fire contains too much oxygen to allow iron to melt; as it approaches its melting point the iron burns instead."http://www.osv.org/cgi-bin/CreatePDF.php?/tour/index.php?L=12&PDF=Y

Pure oxygen is used in oxyacetylene torches to actually ignite burn and melt the steel when cutting. These torches were used to help clear the debris pile during search and recovery operations. A slag of melted and re-solidified steel and Ferrous oxide is formed on the opposite side of the cut. This slag formation and the angle of these cuts were erroneously reported to be evidence of cutter (demolition) charges having been used to sever the columns. Small molten pieces of glowing steel cool into spheres as they fly out from the cut. These steel microspheres,- said to be evidence of thermite,- would also have been produced during the buildings’ construction by welders and retained in the concrete or else where only to be released during the collapse.

The deep seated pockets of fire often have to be dug out by hand tools, back hoes or grapplers in order to expose the burning material for extinguishment. It is common to hold off hitting the fire with water until it is fully exposed in order to prevent the great amount of steam that would be created from obscuring the work area until the fire is fully exposed and can be quickly extinguished. This is what is happening in the picture of a grappler pulling out a piece of glowing hot steel from the debris pile so often described as ‘molten’ steel.

About the “meteorite” recovered from ground zero. Everyone uses the word ‘molten’ in describing the steel in the meteorite when it actually is deformed pieces of the bar joist flooring compacted with concrete and pieces of furnishings. This is careless language. Apparently people seeing steel deformed by heat immediately call it molten or melted steel. Melted or molten steel indicates a liquid state which only occurs at higher temperatures than an ordinary fire can produce. The meteorite is a piece of pancaked concrete and steel floors fused together by high impacts. It contains charred pieces of books and paper which would not be present if heat high enough to melt steel existed at anytime in the “meteorite”.

Much has been made of the presence of molten metal in the debris pile after the collapse. Presumably this molten metal was somehow thought to be connected to explosions or thermite charges, but there were Uninterrupted Power Supply (UPS) battery rooms on some floors of the Towers and Building 7. These battery rooms supplied continuous battery power to computers if the electricity failed for any reason. These batteries contained tons of lead which melts at low temperatures [327 C (621 F)]. The heat from the fires in the debris pile could easily have melted this lead and the aluminum from the plane and aluminum from the tower’s own cladding which were probably the metals that were seen flowing through the pile. NIST reported UPS in the 13th floor of Building 7 and the 81st floor of Tower 2. There were also quantities of lead, tin, silver and even gold used in the computer circuit boards. In the some people’s imagination the reported ‘flowing molten metal’ became ‘rivers of molten steel’.

Additionally the EPA reported over 400 different chemicals in the dust and debris. These chemicals could easily be assembled conceptually to propose any type of chemical reaction imaginable including thermite reactions. In addition thermite reactions are rapid they are over in a matter of seconds and wouldn't last the hours or days at which times the molten metal was observed. As far as I know thermite has never been used to demolish buildings and the expertise probably doesn’t exist. Thermite is hard to control and can’t be held against the columns because it would burn, spall or melt down through any material used to support it against the columns long enough to do enough damage to cause the column to buckle.

About the concrete pulverization into dust reported to be only possible by explosive charges; F.R. Greening did a paper called Energy Transfer in the WTC Collapse in which he says "the energy required to crush concrete to 100 μm particles is 1.9 × 1011 J, which is well within the crushing capacity of the available energy. Hence it is theoretically possible for the WTC collapse events to have crushed more than 90 % of the floor concrete to particles well within the observed particle size range." http://nistreview.org/WTC-REPORT-GREENING.pdf. I would also investigate the possibility that the concrete was sub par to begin with due too much air or water having been added during the pouring and finishing operation to speed working and leveling the cement or to freezing during curing in the course of construction.

Do you think the architect or engineers who built the Towers would want to admit the deficiencies in design, fireproofing and other construction weaknesses after their buildings collapsed? Do you think they will get any other jobs after 4 of their buildings collapsed from fire? How come the 9/11, Architects & Engineers for truth never mention Building 5. Building 5 had a serious fire on many floors and had several floors collapse from the steel beams being disconnected from the columns due to thermal expansion, sagging and catinary action tearing out the bolted beam connections? (ASCE, Building Performance Study) I suppose that some of the ‘truthers’ never even read the American Society of Civil Engineer’s or the NIST’s report. Did building 5 also have charges set beforehand? How many other buildings had hypothetical charges set beforehand and were never set off? If they went to all the trouble to rig all these buildings with alleged explosives, why didn’t they just set them off and forget the planes and the fires. Waiting for the planes and fires would surely increase their chances of being detected.

There are so many questions answered by the fire theories and so many unanswerable questions posed by the demolition theories that it is ludicrous to continue the proposition that explosives had to be employed to collapse these buildings.

Do you know that the Port Authority of NY, NJ didn't legally have to follow any building codes? The reason the columns broke at the splices was that they had serious weaknesses due to lack of reinforcing plates or even welds on most of the exterior column, bolted splices and not because of the ridiculous idea repeated incessantly by Richard Gauge that they were broken up into short pieces, presumably by explosives, ‘so they would fit onto the trucks to be carried away’. The long span truss floors were never tested for fire resistance at their design length. Why do you think it took so long to get the plans for the buildings after they collapsed while the building engineers had them all along? I am sad to think the architects and engineers for 9/11 truth would be accepting of such a convenient excuse,- that explosives or thermite was involved,- but that idea would allow them to avoid the introspection necessary to fully realize their own ignorance of what fire can do to steel beams and columns,- a necessary realization before meaningful knowledge can be developed to make their buildings safe.

About the eye witnesses hearing supposed explosions; there are many reasons that loud sounds can be produced at a fire. Most of the people in Tower 2 did not know Tower 1 had been struck by a plane but they heard the explosion and even felt the radiant heat produced by the fireball. Often at fires the ones closest to the fires and engaged in heavy work have a very limited overall conception of what is actually happening. When you don’t know what’s happening especially in the dark smoky conditions your imagination starts to work. Barry Jennings said he was stepping over dead bodies when being led out of building 7 after it was hit by pieces of Tower 1. He later admitted that he never actually saw these bodies. He must have imagined it. I suppose he also imagined seeing the two Towers still standing amid the smoke after he experienced a supposed explosion while descending the stairway. The “explosion” that Barry Jenning’s heard was probably the pieces of Tower 1 hitting Building 7. Even experienced reporters couldn’t believe the towers were gone from the skyline after they collapsed.

When Tower 2 collapsed most of the people in Tower 1 thought the sounds and vibrations came from the building they were in and they even felt a rush of air up the stairs as the air was compressed in the cellars. The fact that they are in strange circumstances with lack of information, smoke and possibly darkness, and the presence of strange sounds creates a fertile field for the imagination. There can also be real smoke explosions (backdrafts) particularly in fires that have a flammable liquid involved. One elevator shaft that extended into the cellars experienced a fuel-air explosion from the jet fuel spilling down and evaporating in the shaft. There were other fuel-air explosions in the elevator shafts. There could have been floor detachments impacting the floors below and producing loud sounds before any general collapse began. Explosives produce loud distinctive pressure waves that can leave people deaf or blow out eardrums and usually blow out all the windows on the particular floor and in any buildings nearby. This kind of sharp piercing crack was not heard. The windows broken out and marble wall panels detached on the interior of the first floor lobby were probably because of torque or bending forces experienced on the lower floor columns from the plane impacts many floors above. The buildings were reported to sway several feet when the planes hit the towers. In order to let additional light into the lobby these lower exterior columns were fewer and further apart than the columns above. The lower ‘core’ columns in this area were stronger and securely cross braced to compensate for this weakness of the exterior columns in the lobby. This fact was probably responsible for saving the lives of the members of a Ladder Company who were trapped in the stairwell on these lower floors during the collapse. It’s too bad this strength wasn’t continued up the core to the building top. It may have saved many more lives by protecting the stairways. The reports of "explosions" in the cellars were also probably from such column or floor displacements or from jet fuel ignitions in the elevator shafts. If you imbed a stick into the ground and hit it with another stick most of the deformation will be in the ground around the bottom of the stick. There were reports of split walls and ceiling collapses on many floors after the planes hit.

The “mysterious” collapse of Building 7.

How do you think that the alleged conspirators knew that Building 7 would be hit by pieces of Tower 1 which would set it on fire? They would have to know this beforehand in order to set the mysterious explosive charges that allegedly demolished the building. Why did they wait 5 hours while the fires burned before they set off these alleged charges, and how did these so called explosive charges or thermite withstand the fires for 5 hours without igniting and burning off? The NIST computer models show steel beams buckling, sagging floors and disconnection of the beams from the columns and finally failure of one key column which started the global collapse, all from the heat of the fires expanding the long span steel and breaking the bolted shear connections in Building 7.

BBC reporting error on Building 7 collapse.

You may ask “How did the BBC know that the Towers were going to collapse?” The BBC didn't know. Did you ever hear a mistake made by a reporter? Or do you believe everything you are told by a TV reporter in the heat of an emergency? The BBC reporter on the air received an erroneous report that the Building 7 had collapsed before it actually did and reported it well before the actual occurrence. It was a simple mistake.

I can imagine how it happened. In addition to the damage done to Building 7 by the heavy steel column trees that pealed off of the collapsing towers some of these steel columns penetrated the roads and broke the nearby water mains. There was fire on many floors in Building 7 and without water these fires could not be controlled. The collapse possibility was anticipated by the Fire Dept. who ordered the evacuation out of the building and out of a “collapse zone” about 600 feet around the building. Apparently they were the only people who realized the possibility that an out of control fire on multiple floors in a steel framed, long span, open area, office building could cause a collapse. They had just experienced the collapse of two similar buildings trapping and killing many of their brothers. The ‘collapse zone’ was a large area including buildings and streets around Building 7 and clearing this large area of people was a big problem. To get some people reluctant to move swiftly out of the area I can imagine someone saying “the building’s coming down”. A reporter may have heard this and called his boss and told him the building 7 is coming down. The person receiving the call believed the building was already collapsing. It went out over the air as the building had already collapsed before the actual occurrence. The anticipation of collapse was a brilliant call by the Fire Dept. and no lives were lost when the 47 story building collapsed a few hours after the evacuation order was given.

This is a message from Chief of Department (ret.) Daniel Nigro the chief in charge of the fire, addressing the conspiracy theories surrounding the collapse of WTC 7.

Release date: September 23, 2007

Regarding WTC 7: The long-awaited US Government NIST (National Institute of Standards and Technology) report on the collapse of WTC 7 is due to be published at the end of this year (although it has been delayed already a few times [ adding fuel to the conspiracy theorists fires!]). That report should explain the cause and mechanics of the collapse in great detail. Early on the afternoon of September 11th 2001, following the collapse of WTC 1 & 2, I feared a collapse of WTC 7 (as did many on my staff).

The reasons are as follows:

1 - Although prior to that day high-rise structures had never collapsed, the collapse of WTC 1 & 2 showed that certain high-rise structures subjected to damage from impact and from fire will collapse. 2. The collapse of WTC 1 damaged portions of the lower floors of WTC 7.3. WTC 7, we knew, was built on a small number of large columns providing an open Atrium on the lower levels. 4. Numerous fires on many floors of WTC 7 burned without sufficient water supply to attack them.

For these reasons I made the decision (without consulting the owner [Larry Silverstein], the mayor or anyone else - as ranking fire officer, that decision was my responsibility) to clear a collapse zone surrounding the building and to stop all activity within that zone. Approximately three hours after that order was given, WTC 7 collapsed.

Conspiracy theories abound and I believe firmly that all of them are without merit.

Regards, Dan NigroChief of Department FDNY (retired)

On October 4 2001 Chief Nigro said; “The most important operational decision to be made that afternoon was the collapse [of Tower 1] had damaged 7 World Trade Center, which is about a 50 story building, at Vesey between West Broadway and Washington Street. It had a very heavy fire on many floors and I ordered the evacuation of an area sufficient around [building 7] to protect our members, so we had to give up some rescue operations which were going on at the time [under the ruble of Tower 1] and back the people away far enough so that if 7 World Trade Center did collapse, we wouldn’t lose any more people. We continued to operate on what we could from that distance and approximately an hour and a half after that order [to evacuate the building and collapse zone] was given, at 5;30 in the afternoon, 7 World Trade Center collapsed completely. I continued to operate at the scene until probably somewhere around 8 o’clock, at which time I borrowed Chief Meyer’s car, because mine was destroyed and went home to [take a], shower, change my clothes and I came back to work at approximately between 11 and midnight with Chief Turi.” (New York Times interview Date; October 24, 2001 , transcribed by Elizabeth F. Nason)

If you really believe that all the top fire protection engineers from the American Society of Civil Engineers (ASCE) and government scientists from National Institute of Standards and Technology (NIST) investigating the collapse are in on a conspiracy and also want to accuse the BBC, the NYC Fire Department, the NYC Police Department, the Red Cross and all the Government agencies controlling access Building 7 of being ‘in on’ a secret controlled demolition even though there was no hard evidence than I would say you may be suffering from a case of paranoia. Paranoia can easily become contagious when people panic and no longer trust their government. We certainly had reason not to trust our previous government. I would say that if you really believe these preposterous demolition theories you should do some soul searching and possibly seek some therapeutic help.

In conclusion I think all the reports of controlled demolition can be explained by sounds or sights produced by the plane impacts and jet fuel and air explosions; the sounds of the Towers collapse. When the interior of building 7 collapsed it would have produced loud sounds well before the exterior walls began collapsing.

It’s an ill wind that blows no good and the good thing is that NIST now has an effective computer model to test whether a new or existing building is safe from collapse from fire. The architects and engineers should use this capability to assure any proposed or existing designs are safe. Another good thing is that any corrections proposed can be run through the computer and any tested for effectiveness. This NIST computer work,- which modeled the fires and every steel column and beam with their connections,- shows that Building 7 was deconstructed by the heat of the uncontrolled fires expanding the long span steel floors, buckling beams, disconnecting structural steel connections, collapsing the floors and eventually buckling one key column which started the progressive collapse. The connections and lateral support were so week that that the collapse of one key column progressed across the core to take down the entire interior of the building. Now that’s an architectural and engineering problem. I want to hear what the Architects & Engineers for 9/11 truth think about a building that can loose one column which starts a progressive collapse that brings down the whole building. Design problem? They should be eager to get those computer models working instead of raving about some imaginary explosives having brought down these buildings.

Exactly - "truthers" reason just like creationists or Holocaust deniers. It doesn't matter how much evidence is presented, or how much bogus evidence is discredited - they are still sure there was a conspiracy. The thing that amazes me is that so many smart people have bought into the 9-11 "truth" movement.

A critical evaluation of the evidence used to prove explosive demolition consists of the following: 90% eye witness accounts/photographic evidence and 10% published articles in The Journal of 9/11Studies and other open source journals including “The Open Civil Engineering Journal”. So, what do we find in these journals? Let’s look at one example.

In an article published in the “The Open Civil Engineering Journal” (Fourteen Points of Agreement with Official Government Reports on the World Trade Center Destruction – 2008, Volume 2) Mr. Steven Jones writes, “Probing for residues from pyrotechnic materials, including thermite in particular, is specified in fire and explosions investigations by the NFPA 921 Code” [page 39].

There is only one problem here: this statement does not exist in NFPA 921.

The exact quote, on page 85, NFPA 921 states: “Thermite mixtures also produce exceedingly hot fires. Such accelerants usually leave residues that may be visually or chemically identifiable. Presence of remains from oxidizers does not, in itself, constitute an intentionally set fire”.

Mr. Jones goes on to state in his article, “The code specifies that fire scene investigators must be prepared to justify an exclusion”. The implication is an investigator should look for these residues, and if the investigator does not, he/she has to justify the reasons for this action.

Again, no where in NFPA can you find this statement.

NFPA does state, “The scientific method, however, should be applied in every instance” (page 7).

I submit that if the quotes used to support a point of view do not exist in the document being quoted, and statements are used which do not exist in the source material, the quality of the research is at best, suspect.

There is one thing for certain: the scientific method is not used in any of the 911 research I have reviewed.

First, I thank Chief Scheuerman for his detailed comment. As a former firefighter and chief officer myself (on a volunteer department which sent rescuers to the WTC site a few days after the collapse) I appreciate his thoughts.

I have myself fought structure fires in which metal components flat out melted. For example, some decades ago we fought a fire in an experimental house built by Alcoa identical to this one. Melted aluminum dripped down into the basement and hit the pooled water from firefighting there and solidified into what look like Hershey's kisses.

The house was insulated with a plastic foam and the fire was fed by ruptured natural gas lines until we could get them shut off, and it defied water streams -- we put 60,000 gallons of water on the fire and didn't put it out. Our interior attack (I was the company officer on the first engine in) on what initially appeared to be a room-and-contents fire was quickly pushed back out and we were reduced to surround and drown with master stream devices and hand lines, except that we couldn't even drown the damned thing. It was the most frustrating fire I ever fought.

On another occasion we had a grain elevator fire in which the flames were every color of the rainbow from the materials involved, including metals like copper, aluminum, and magnesium, and we found pools of once-molten metal in the residue of that fire, too.

So just seeing unidentified molten metal would not indicate a thermite or explosives initiated collapse. The examples I sketched are not at all comparable to the scale of the WTC event, but they illustrate that even 'small' fires produce more than enough heat to melt many metals. All the metal used in construction is not steel.

Amateur conspiracy theorists rarely have direct experience or knowledge of the matters they blather on about.

"The thing that amazes me is that so many smart people have bought into the 9-11 "truth" movement."

Think of the 9/11 movement as a socio-political movement. Notice how many of those leading advocates were either already believing in other conspiracy theories, or were very far left (marxist or anarchist), or very far right.

The relative popularity of their claims are due to two reasons. The first is the internet, and video uploading. I'm sure that moon landing conspiracies would have bee much more prevalent in the 70's and 80's if the proponents had the ability to construct slick looking documentaries which could be seen by millions. The second is that there was a lot of resentment towards the Bush administration, conservetives, the war, and the government in general. Notice how the conspiracy movement didn't pick up steam until around 2005 and 2006. After the invasion of Iraq.

Obama changes everything. He's well liked and respected, and he's winding the war down. This, combined with the excellent refutations provided by scientists and skeptics means that their movement is dying. Only the diehard conspiracists will remain.

Please tell me that this talk was video taped. It'd be the perfect video to put online to add to the collection of Truther refutation videos.

Mark:

NOVA has done two episodes on the collapse of the buildings. The first was the 2001 (or 2002?) ep "How the Towers Fell". In 2006, they did an updated version called "Building at Ground Zero". Both are good, but the first episode was based on incomplete data and initial draft reports, so the 2006 episode is superior.

None of what Craig has said explains symmetrical collapse at free-fall speeds. Arthur Sheuermans long winded post does nothing to explain this either. No one in the truth movement is arguing the possibility of damage caused by prolonged exposure to high temperatures. What they are arguing is the existence of those prolonged high temperatures and their ability to cause the fore mentioned symmetrical collapse at free-fall speeds.

Let's think about this for a second. What would it take for a building to collapse at every corner simultaneously? A simultaneous failure of every support structure involved. The fires involved would have had to have been burning at equal temperatures, through out the effected area, for every support to fail simultaneously. Were buildings 1,2 and 7 burning in such a manner to cause this kind of failure? No. And that's not even taking into account the damage caused by the impact of the planes because, even simple logic dictates, that a structure will tend to fall towards its most damaged side first. Which none of the 3 buildings do.

Look at the video footage of building 7. It's called "The Smoking Gun" of 9/11 for a very good reason. The fires involved were only burning on 4 of 47 floors opposite the side impacted by the debris from building 2 and were only visible from that side. So please, explain to everyone here, how localized fires alone could cause building 7 to collapse symmetrically at free falls speeds? It couldn't.

You dismiss eye-witness testimonies as unreliable and that's totally understandable. The problem the truth movement has is that there is a LOT of eye witness testimony reporting the presence of molten metal at ground zero and the presence of explosions BEFORE the collapse of all 3 buildings. The explosions were even reported by the news the day of the attacks and in countless interviews with first responders. And yet none of the 4 investigations of 9/11 mention even the possibility of explosives. The director of NIST even went so far as to admit they never even looked for explosive evidence. But I guess that is also understandable as the first investigation, the 9/11 Commission, didn't even start until nearly a year and a half after the attack and well after ground zero had been cleared of debris (i.e. evidence.)

The 9/11 commission looked at the evidence. The evidence didn't suggest to competent people that there were explosives.

As for WTC 7, it simply doesn't make any conspiracy sense. If you're going to hire people to fly planes into the twin towers, why would you also load a *different* building with explosives and bring it down hours later?

As usual, the truthers have no coherent narrative of their conspiracy.

But the fact that NANO-Thermite was found in at least 4 dust samples was not discussed. Although it can be claimed that all kinds of materials were found in the building that does not means that they would spontaneously come together to represent something extremely organized. Since all the components and materials of a car were present if we collapsed the buildings a billion times they would not form a car at the bottom or even a simple am radio. It is just as ridiculous to say that precisely uniformly sizes NANO composites, with uniform particle distribution, with all pieces found all have precisely the same composition and uniformity, would miraculously appear scattered thought out the debris dust. Bottom line nano-thermite should have never been found at the WTC sites. Miracles do not happen and the laws of physics still apply

I agree, the debate was well hosted and refereed. Thanks to all who made it possible, and hopefully there will be more public discussion like this in the future!!

The biggest "clincher" for me pertaining to the twin tower collapses is this: the presence of molten metal and hot fires for weeks after 9/11. There is more than ample evidence and testimony for this fact, including the testimony from the mayor of NY City Giuliani himself! I was shocked and amazed when Craig denied this fact of molten steel and the testimonies of it. (Much more about this evidence is available on the AE911Truth.org website.)

Nobody who is sensible will debate that office fires can completely melt steel. So, that simply leaves us with two facts: molten steel, no explanation.

"9/11 Truthers" are indeed intelligent people who are looking for an explanation that considers not just convenient ones, but ALL of them. Occam's razor in all its purist scientific glory! Thus, we push for a new 9/11 investigation.

Because Giuliani, the Mayor of NYC, saw the hot fires at Ground Zero weeks after 9/11. Therefore he is a witness, and his testimony should examined and accepted or explained. But not ignored. It doesn't take an expert to see a hot fire burst out, does it?

And let's not forget here the many other separate testimonies of first responders that corroborate Giuliani's account.

Don't you believe in the importance of testimony? Or do you simply cherry-pick the testimony you want to believe, if it fits your view?

I know you may not realize this yet, but I'm sure your readers will understand the total absurdity of your claim that Giuliani lied about spontaneous hot fires igniting at Ground Zero on 9/11. I can't imagine why he do that! So that people would ask questions about the source of those "imaginary" fires? Crazy!

Or perhaps... the fires he described were actually there (gasp!), simply mentioned as part of his account of events. (A slip-up in hind sight for sure, but an innocent mistake.) Hmm... That seems much more likely, eh?

Instead, sir, you have shown yourself to be a first-class cherry-picker. Well done!

No - I have no idea what Giuliani saw or didn't see. I just find it absurd to claim he saw molten steel, when you have no evidence that he could distinguish molten steel from other molten metal. If you have such evidence, present it.

You also agree that the government lies to it's people.

Now you're just being moronic. Giuliani does not equate to "the government". And of course members of the government lie. But 9/11 has been examined to death by independent investigators, and there is still no good evidence of a US government conspiracy. The evidence for explosives is nil. The evidence for remote-controlled planes is nil.

Instead, sir, you have shown yourself to be a first-class cherry-picker. Well done!

To clarify: Giuliani testified that hot fires - not molten steel - would spontaneously ignite and burst out all over Ground Zero. That's a fact. I don't think he lied about that, nor do you I presume. But where did those hot fires (~2000 F) come from? And how? Explain to me the science behind this testified account, please. And not just this account, but many similar others.

"Pieces of steel have also been found that were apparently melted and vaporized..."

"Perhaps the deepest mystery uncovered in the investigation involves extremely thin bits of steel collected from the trade towers and from 7 World Trade Center, a 47-story high rise that also collapsed for unknown reasons. The steel apparently melted away, but no fire in any of the buildings was believed to be hot enough to melt steel outright."

Do you still disbelieve that steel was melted in those buildings? If not, "how?" is surely the logical question we all have! And in 3 buildings! On 1 day!! From fires?!? This question has not found a scientifically viable answer; it's simply denied or ignored.

Do you still think there is absolutely no reason for another investigation into the issue of molten steel at Ground Zero? If so, how can this be?? Hasn't your intellectual curiosity been piqued at all?

I don't accept that there was "molten steel". No good evidence has been presented that there was.

I don't accept that the presence of "molten steel" means there was a bomb. No good evidence has been presented for this deduction.

I don't accept that Giuliani is a reliable witness about anything. He's not a metallurgist.

I don't accept eyewitness testimony that is not backed up by good forensics.

I don't accept the claims about "nano-thermite", because the evidence in support of this claim consists of a single article by unreliable people who overlook obvious alternative explanations, and because thermite is completely inconsistent with what we know about the attack.

I don't accept the claims about WTC 7 because the truthers have no coherent narrative of why government conspirators would want to bring down a building that was evidently not hit by the planes.

Satisfied?

Now, on your side, where's the coherent narrative of the attack? Where's the justification for claims of molten steel?

I don't accept that Giuliani is a reliable witness about anything. He's not a metallurgist.Nobody said he was! But I think he can identify a fire when he sees one.

I don't accept eyewitness testimony that is not backed up by good forensics.Then you do not understand criminal law, where corroborating testimonies are typically the critical piece of prosecution. See my next point as well.

Where's the coherent narrative of the attack?I refuse disperse any narrative of the attack because I have neither the means nor the authority to do so. (That's why we're calling for a new authoritative investigation to actually analize the many ignored facts.) All I know is that there are holes the size of trucks in the official narrative; like the hot fires for weeks at Ground Zero, as a simple example.

Satisfied?

No, I' not satisfied. Your question about how Giuliani knew the temperatures of the fires is a red herring - there are dozens of possible ways! You pick.

You still haven't told me why Giuliani would lie about spontaneous hot fires igniting all over Ground Zero. Care to elaborate???

I am keeping this argument extremely simple for you to show you that you will even deny or reject the plain-sight evidence and testimony laid before your eyes. No rational debate is possible with someone like that.

And thank God our Justice system isn't in your hands. You seem to want a verdict before a legit trial of evidence.

You just keep citing the same claims: they talk about "molten metal" and sometimes steel - but there is no proof that the metal was steel. Where are the lab reports analyzing the "molten metal"?

where corroborating testimonies are typically the critical piece of prosecution.

And you don't understand that eyewitness testimony is notoriously unreliable, as proven in case study after case study.

I refuse disperse any narrative of the attack because I have neither the means nor the authority to do so.

Incoherent babble. And, as I have pointed out, truthers have no narrative of their conspiracy that makes sense.

You still haven't told me why Giuliani would lie about spontaneous hot fires igniting all over Ground Zero.

I never said he lied about that, so stop pretending I did. I said I wouldn't trust him on anything. Who knows if he was reporting what he saw or what someone told him? And if there were fires, so what? No one disputes the fact that there was a large amount of combustible material available. Really, you make no sense at all.

here are dozens of possible ways! You pick.

Moronic. You're making the claim, so the burden of proof is on you to provide the evidence.

You just keep citing the same claims: they talk about "molten metal" and sometimes steel - but there is no proof that the metal was steel. Where are the lab reports analyzing the "molten metal"?Great question! I wish I knew the answer. And I keep citing testimony because you don't provide reason to discredit them all. Fine - molten "metal" - where did it come from? And how did it stay hot for weeks? Same questions. Let's push for an authoritative investigation and get some answers, shall we? It's almost like we're on the same side here or something.

And you don't understand that eyewitness testimony is notoriously unreliable, as proven in case study after case study.Notoriously unreliable? Hogwash! Yes, it is occasionally unreliable in some incidents, but not nearly to the extent you are claiming, and not with vast amounts of witnesses. Throw out testimonies from court cases -- is that what you suggest? It's an excuse to cherry-pick the evidence you believe.

I said I wouldn't trust him on anything.Cherry-picking

And if there were fires, so what? No one disputes the fact that there was a large amount of combustible material available.We are talking about HOT fires here. You know, like "melting (not just weakening) metal" level of temperature here. AND FOR WEEKS. THAT'S the big deal, and you know it. Is that why you deny it? If so... cherry-picking.

Moronic. You're making the claim, so the burden of proof is on you to provide the evidence.Ok then, let me help you. Hmm... maybe a first responder TOLD him the temperature of the fires and/or the molten metal causing them. Possibly?? Probably?? Seriously, you are becoming ridiculous with your pathetic games.

But given your previous responses to my simple questions on hot fires, I have neither the time nor patience to discuss any other facts with you. Not until I'm satisfied that you can logically accept the presence hot fires and molten "metal" for weeks at Ground Zero. Otherwise, it's pointless.

Then why are you bothering?Good point. I'll consider this by your next reply. Maybe I simply shouldn't be wasting my keystrokes with you. I hoped you would come around to reason and logic, but I see now that you can't - or won't?

Good - you agree with me that there is no conclusive evidence about "molten steel".

Hmm... maybe a first responder TOLD him the temperature of the fires and/or the molten metal causing them.

If that's your claim, then produce the evidence for it.

Fine - molten "metal" - where did it come from?

If there was molten metal, it could easily have been metals with low melting points from the debris of the buildings.

no less than 60 per cent of the 9/11 commissioners have now publicly stated that the government agreed not to tell the truth about 9/11 and that the Pentagon was engaged in deliberate deception about their response to the attack?

Your evidence for this is what? A comment on a prisonplanet blog? Let's have a list of the names and their statements, not unverified claims on a wacky website.

I have neither the time nor patience to discuss any other facts with you.

You can't argue with truthers - they are convinced of a US government conspiracy despite the abundant evidence that it was Al Qaeda. Read The Looming Tower.

A comment on the "molten metal" business. I was a volunteer firefighter for 30+ years. 20-odd years ago we fought a fire in an experimental aluminum house built by Alcoa, the so-called CareFree house, of which they built 40. The house was insulated with plastic foam, and only the interior furniture and area rugs were Class A fire fuel. The fire was apparently started by a leaking natural gas line in the kitchen that was somehow ignited, probably from the stove pilot light. That's based on the location and appearance of the fire on arrival of the first fire company on the scene. The gas flame in turn apparently melted through an aluminum partition and ignited the plastic foam insulation.

That was the single most frustrating fire I have ever fought, and I've fought some frustrating fires, e.g., a grain elevator fire where we were on the scene for 36 hours. I was on the first engine in to this house fire and was the first officer who entered the house with a crew with a hose line, and the fire appeared to be confined to the kitchen area of the open-design first floor, mostly visible in the area of the gas stove.

Because the householder and her dog were safely out in the front yard, we immediately began fire suppression operations with hose lines and water flow that would have knocked down a similar fire in a wood frame house in single digit minutes. But we put 60,000 gallons of water on that single-story house (with full open basement) and we could not put it out. It burned itself out.

Afterward we found pellets of molten metal in the basement debris, some of them shaped like Hershey Kisses from molten metal melted by the intensity of the fire dripping into the water in the basement and cooling rapidly. I still have one as a souvenir. Amateurs ought not blather about stuff of which they're ignorant.

I find the truther obsession with "molten metal" truly bizarre - as if there were no sources of combustion in the WTC towers that could burn hot enough to melt metals such as aluminum and and magnesium which were probably present.

And similarly with "hot fires" - in such a volume of material, why would it be unlikely that some fires would continue to burn for days?

@RBHThanks, I appreciate your comments and your service as a volunteer firefighter for 30+ years. I would expect that someone more rude and idiotic than I to flat-out refute documented testimony here or elsewhere.

But I would certainly not do a thing like that. i.e. I'll simply trust who you say you are. And what you say you saw. Benefit of the doubt, as they say. Testimony is a very valuable piece information in my books.

Let me be honest with you here, and tell you that I am a software engineer, not qualified to give an expert opinion about building fires or collapses or metal droplets; instead, I refer people to the testimonies of those who are qualified, and who saw many amazing things on 9/11 that haven't been officially explained or accounted for yet. In fact, I've done this repeatedly here on this blog post, to no seeming avail.

I am indeed amazed by your claim that you found molten metal drops in the debris of the inferno you fought. But I won't even deny or dismiss that fact. I trust your testimony because I believe that you have experience and nothing to gain from lying.

Would you then also agree that molten metal was probably found at Ground Zero? And that it even remained very hot for weeks after 9/11?

Would you then also agree that molten metal was probably found at Ground Zero? And that it even remained very hot for weeks after 9/11?

Given the volume of material from the towers on the ground it wouldn't surprise me at all that the fire burned in the debris for days or weeks. And the finding of melted metal remains wouldn't surprise me a bit either. Whether it was still molten -- i.e., still liquid -- weeks later is not clear to me from the reports. That I'd have some doubts about.

Incidentally, my department sent a 4-man specialist S&R team to the site just two days after the towers collapsed. They saw nothing in the week they were there that made them think that anything but what was reported at the time happened -- aircraft impacts on the towers with the structural failures attendant on fuel fire weakening the structure. In the photographs of the scene it's clear that the fires were well-ventilated and thus burned very hot.

Not until you explain, in a coherent way, why molten metals of low melting point cast any doubt on the generally-accepted account of what happened.So, after I do explain it to you in a coherent and simple simple way for you, you'll agree to sign the petition for a new investigation? Did I read that right? Is that what you are saying?? If so, I'd be happy to.

Watch 7 come down.Watch all the videos of the collapse, there are many of them. Free fall speed...admitted to by NIST.Molten metal for weeks under ALL THREE bldgs.Where are the center collumns?Dozens of witnesses claiming there were "explosions"."News" reporters announcing explosions."Waterloo"?You people are exhibiting a pathological level of denial.

In fact: Your assertion has NOT been adequately addressed scientifically in the public discourse of 9/11 events.

"Jet fuel is more than adequate to melt many metals that were in the structures."

This is a highly deceptive comment. Of course SOME fuels can melt SOME metals. But jet fuel is a kerosene fuel. Look it up. It is not able to significantly weaken construction-grade steel (which was tested and approved by Underwriter Laboratories), let alone melt it. Furthermore, all metal wicks away/disperses heat. Therefore, the localized, organic fires moving around on a few floors cannot take down a building -- in a symmetrical, smooth descent -- as was witnessed on 9/11. IMPOSSIBLE.

Need more examples? Look at this recent building fire in China. I would like you to compare the buildings, and then explain to me why a ratty communist apartment building under renovation did not collapse from an 8-hour inferno, but 2 award-winning American buildings did after two hours on 9/11. And a third building that afternoon. For the first and last time in history. Seriously, explain all of this. :)

Also, your denial of the vastly large melted steel at the base of all three towers for weeks after the demolition -- both photographic evidence and witness testimony -- IS truly pathological.

McCormick Center fire (!!NOT!! a high-rise steel building, but an exhibition hall!)click to see

In conclusion: I'm still patiently waiting for you to find your critical thinking cap, which you proudly profess to posses everywhere on your blog. When you do, let me know and we'll continue to explore important unresolved issues and justice that can heal this country.

Serval witness testimonies of molten steel at Ground Zero, including several members of NYFD:

You're kidding, right? You can't just look at molten metal and say "Hey, that's steel." Most metals look alike, and molten steel doesn't like substantially different from any other molten metal. Without testing, it would be impossible to know if the metal was steel.

As for critical thinking, I see no sign that you, nor any other truther, is capable of it. No truther has even given any viable scenario for why the government would both (1) set explosives and (2) attack with planes when evidently (1) would suffice.

Here is a common sense question: If an entire skyscraper can be destroyed and pulverized into dust by fire alone in a few hours, then why would demolition companies need several months to rig it with explosive charges to bring it down? Wouldn't they be out of business since all that trouble could be saved by just lighting a few floors on fire for a few hours? Duh.

The jet fuel at best could only ignite office fires, which are about 1000 degrees Farenheit and far from the 2700 degree temperature required to melt steel. But even if it did melt the steel or caused it to weaken, still, it would not have caused the huge structural resistance underneath it to implode with no resistance and pulverize the concrete to dust. There is no basis for that. No miniature models have ever been able to replicate this.

A building on fire deforms gradually and unevenly. And if parts of a building collapse, they will topple OVER to the side, not fall symmetrically straight down. That's a key point that the 9/11 propagandists can't explain or address. Not one 9/11 anti-conspiracy site has ever explained how fire could cause such a rapid collapse with no resistance from the structures. They can't because it's not possible to do so. Therefore, the authors of these anti-conspiracy sites must be either delusional, ignorant or agenda-driven. Many internet debunkers could also be paid shills and trolls. Google "FBI Cointelpro" to find out how the FBI has run infiltration programs on the internet.

What the anti-conspiracy propagandists do is use cheap red herrings to try to dodge the fact that they can't explain this collapse. For example, they use the onset of the WTC and Building 7 collapse to add a few seconds to the time of their collapse, using those few extra seconds as a basis to try to discredit the notion of "free fall". But this is an irrelevant red herring, because the fact is, adding extra seconds to the collapse time does NOT change the fact that fire absolutely CANNOT account for this collapse in any way at all. In fact, fire cannot account for any of the 10 key features of the collapse (see AE911Truth.org for a description of all 10), whereas the controlled demolition hypothesis can.

The masterpiece film by AE911Truth.org entitled "9/11 Blueprint for Truth" (which you can see on YouTube or at AE911Truth.org) goes over this point by point using the scientific method. Their new film "9/11 Explosive Evidence - Experts Speak Out" (also available on YouTube) is a must see and clincher. It features 50+ highly credentialed architects, engineers and scientists who explain why the official fire collapse theory given by the government and media has been totally debunked and why a new objective investigation is needed.

In contrast, NONE of the apologists of the official 9/11 story that debated Richard Gage (Founder of AE911Truth.org) on various radio shows (including Coast to Coast AM) were ever able to explain how fire accounted for all the data. Not one. All they did was use red herrings to try to nitpick Mr. Gage's hypothesis, but offering no hypothesis of their own. This can only mean that their job was to discredit rather than to find the truth. Even if they were to prove Mr. Gage wrong (which they didn't) it would still not prove their fire collapse case. These apologists have also used lies and false facts. For example, Ron Craig claimed that the collapse of the Delphi building was the same type as the WTC collapse. Yet any cursory viewing of that collapse on video shows that it wasn't and that he was wrong. But as we've seen before, parroting false facts and lies is typical of anti-conspiracy propagandists.

If an entire skyscraper can be destroyed and pulverized into dust by fire alone in a few hours, then why would demolition companies need several months to rig it with explosive charges to bring it down?

Possibly because they want it to collapse neatly into its own footprint, and not take half a city block around it? Duh.

(I know, I shouldn't waste time on fools. But that was too obvious to pass up.)

Amen Winston! This blogger is either full of bunk or guile. The experts have spoken out, and the evidence needs to be investigated. WTC7 free-fall acceleration = massive removal of building material simultaneously. Period.

Winston Wu said "If an entire skyscraper can be destroyed and pulverized into dust by fire alone in a few hours..." Actually, as I understand it, the WTC towers were destroyed not by fire alone, but by large planes crashing into them at high speed. Demolition companies probably can't afford to crash planes into structures they wanted to demolish. (I could be wrong, though.)

Also, NIST admits that the planes' impact did not have anything to do with the Twin Towers collapses, as they stood for aprox. an hour afterward that, and finally collapsed long after the jet fuel had been all burned up. (Think of the Chrysler building.) Therefore NIST claims office fires caused the skyscrapers to collapse symmetrically, which is just silly but people believe it anyways. If I'm wrong give me examples where fires have totally brought down skyscrapers (besides on 9/11).

@annonymous -- "Demolition companies probably can't afford to crash planes into structures they wanted to demolish." Think how easy it would be to smash few skyscraper columns and then light some fuel on a couple of floors. Demolition companies would be out of business once the word gets out! Keep this a secret please. No?

@Shallit - You have STILL not explained the free-fall acceleration of WTC7. I'm waiting!

Now let me correct my misstatement: According to NIST the planes' impact did not cause the Twin Towers collapses. In fact the [[impossibly]] hot office fires were essential to taking down the Twin Towers which would not have collapsed otherwise.

NIST’s findings also do not support the “controlled demolition” theory since there is conclusive evidence that:

-- the collapse was initiated in the impact and fire floors of the WTC towers and nowhere else [[that's false because there was a huge explosion in the lounge and bombs in the basement; but even IF so.. so what?!? demolitions can be engineered from the bottom up, inside out, or from anywhere else.]]

-- the time it took for the collapse to initiate (56 minutes for WTC 2 and 102 minutes for WTC 1) was dictated by (1) the extent of damage caused by the aircraft impact, [[this is interesting -- did the plane use its kinetic energy to strip off the fireproofing, or to damage massively thick columns?]] and (2) the time it took for the fires to reach critical locations [[what about temperatures??]] and weaken the structure [[NIST never released any of their computer data models for scientific verification]] to the point that the towers could not resist the tremendous energy released by the downward movement of the massive top section of the building at and above the fire and impact floors. [[office fires don't get hot enough to weaken steel buildings to totally collapse; perhaps partially (tipping over, etc.) but that's all. it's never happened before or after 9/11. ps if the towers had tipped I would have believed NIST's conclusions.]]

Video evidence also showed unambiguously that the collapse progressed from the top to the bottom, and there was no evidence (***collected by NIST or by the New York City Police Department, the Port Authority Police Department, or the Fire Department of New York) of any blast or explosions in the region below the impact and fire floors as the top building sections (including and above the 98th floor in WTC 1 and the 82nd floor in WTC 2) began their downward movement upon collapse initiation. [[that's a big big LIE; look at the huge ejection squibs! and the melted metal pooring out of the building just minutes before collapse! with the eye witness molten metal accounts, and photographs, and temperature maps!]]

In summary, NIST found no corroborating evidence for alternative hypotheses suggesting that the WTC towers were brought down by controlled demolition using explosives. [[they later admitted that they never LOOKED for this, so of course they never found it. just read *** again. This is science?!?? The NIST report flies in the face of science.]]

1) How come it hasn't collapsed into its own Footprint, they do in New York ???!!!

2) Oh, i thought towers were meant to collapse when they caught fire!

3) It will be interesting to see if this modern,high-rise,steel-framed building will collapse in its own footprint with a pyroclastic wave as a result of a fire, thus demonstrating the credibility of it having happened to towers 1, 2 and 7 in New york, 2001.

7) Oh look another one that hasn't had a pinpoint perfect free-fall collapse from a bit of heat.

8) The engineers of the 9-11 controlled demolition must be feeling verrryyy uncomfortable right now.

9) Don't bother me until you've video of the building collapsing upon its own footprint at free-fall.

10) Yea, don't buildings automatically collapse when they catch fire? Isn't that what they do to demolish buildings - just set them on fire and they collapse into their own footprint, no prob.